首页 | 本学科首页   官方微博 | 高级检索  
文章检索
  按 检索   检索词:      
出版年份:   被引次数:   他引次数: 提示:输入*表示无穷大
  收费全文   551666篇
  免费   60177篇
  国内免费   783篇
  2021年   5179篇
  2018年   6210篇
  2017年   5842篇
  2016年   8548篇
  2015年   12673篇
  2014年   14554篇
  2013年   19085篇
  2012年   23022篇
  2011年   23078篇
  2010年   15182篇
  2009年   13853篇
  2008年   20011篇
  2007年   20478篇
  2006年   19279篇
  2005年   18244篇
  2004年   18178篇
  2003年   17041篇
  2002年   16464篇
  2001年   20351篇
  2000年   20054篇
  1999年   16407篇
  1998年   6917篇
  1997年   6522篇
  1996年   6222篇
  1995年   5968篇
  1994年   5522篇
  1993年   5578篇
  1992年   13312篇
  1991年   13134篇
  1990年   12904篇
  1989年   12339篇
  1988年   11470篇
  1987年   10793篇
  1986年   10293篇
  1985年   10223篇
  1984年   8620篇
  1983年   7492篇
  1982年   5861篇
  1981年   5280篇
  1980年   4970篇
  1979年   7860篇
  1978年   6467篇
  1977年   5734篇
  1976年   5407篇
  1975年   6127篇
  1974年   6736篇
  1973年   6543篇
  1972年   5755篇
  1971年   5341篇
  1970年   4541篇
排序方式: 共有10000条查询结果,搜索用时 16 毫秒
101.
John L. Graner 《CMAJ》1985,133(9):855-857,880
In 1849 Thomas Addison described the clinical entity now known as pernicious anemia. In 1855 he reported several cases of adrenal insufficiency, or Addison''s disease. Considering the importance of these works, there remains a great deal of confusion about them. Contrary to what many historians have written, a review of Addison''s original publications demonstrates a firm appreciation of the distinction between pernicious anemia and adrenal insufficiency, based particularly on the discoloration of the skin in these conditions. Three major sources of possible confusion for historians who are attempting to understand Addison''s views include Addison''s early attempts to link pernicious anemia with disease of the supra-renal capsules, Addison''s redefinition of pernicious anemia in his monograph on adrenal disease, and several confusing statements made by Wilks and Daldy in the first reprint of Addison''s monograph.  相似文献   
102.
Binomial parameters of transmitter secretion were calculated on the basis of analysis of synaptic potentials in the frog sartorius muscle. Negative values of the parameter p were found in some synapses. This happened most often in low Ca2+ concentrations and with low amplitude of miniature end-plate potentials. The results were interpreted in terms of a model assuming spatial heterogeneity of probability of transmitter quantum release at different release points. Simulation of transmitter secretion by computer showed that the appearance of negative values of the parameter p and incorrect estimates of n experimentally are connected with the form of distribution of probability of transmitter quantum release in the synapse and with the amplitude of miniature potentials.S. V. Kurashov Kazan' Medical Institute, Ministry of Health of the RSFSR. Translated from Neirofiziologiya, Vol. 16, No. 2, pp. 182–189, March–April, 1984.  相似文献   
103.
Forty-two white-rot fungi isolated in South America were incubated with long fibre sugar cane bagasse (LFB). The residual composition of LFB was determined after white-rot decay at 30 and 60 days. The ratio of residual lignin to residual lignin to residual cellulose (RL/RC) of untreated material (LFB) was 0.48. After white-rot-decay, the residual material with lower RL/RC ratios indicated that mainly lignin was degraded. In only 30 days, Phlebia sp. MVHC 5535, Athelia sp. MVHC 5509 and Spongipellis pachyodon MVHC 5019 caused a decrease in the RL/RC ratio to 0.36, 0.37 and 0.38, respectively, while it took 60 days for Ganoderma applanatum MVHC 5347, Hyphodontia sp. MVHC 5544, Panus tigrinus MVHC 5400, Stereum sp. MVHC 5113, Phellinus punctatus MVHC 5346 and MVHC 6388 to reach a ratio lower than 0.40. No correlation was found between the amount of some ligninolytic enzymes secreted and the residual composition of bagasse after white-rot fungi fermentation. Most of the fungal strains caused an increase in the relative amount of residual cellulose, indicating that hemicellulose was the preferred energy source.  相似文献   
104.
Extensibility, contractile function and resistance to excess calcium of the right atrium myocardium were studied in normotensive Wistar-Kyoto and August rats and in spontaneously hypertensive rats (SHR). It was shown that long-term stress results in a decrease in the measured parameters in normotensive animals. SHR do not show any stress-induced disturbances. It was discovered that in intact SHR rats, the myocardium has a greater resistance to excess calcium, indirect evidence for higher efficiency of the Ca-pump of the sarcoplasmic reticulum in cardiomyocytes of SHR animals, which is apparently a constituent part of the mechanism of such animals' heart increased resistance to stress-induced damage.  相似文献   
105.
THE TIMING OF DIVISION IN CHLAMYDOMONAS   总被引:3,自引:2,他引:1  
  相似文献   
106.
The neutrophil-stimulating properties of 38 S. aureus strains and 32 S. epidermidis strains were studied in the reaction of luminol-mediated chemiluminescence. All S. aureus strains and 29 S. epidermidis strains were found to possess neutrophil-stimulating activity, the mean activity index for S. aureus being significantly higher. The stimulating activity of the strains varied within a wide range (the variation coefficient was 120.0 +/- 21.9%) and did not correlate with the content of protein A in bacterial cells and the degree of their hydrophoby. The opsonization of staphylococci with normal human serum enhanced the neutrophil reaction 1.5- to 100-fold and simultaneously leveled out the chemiluminescence indices in experiments with different strains (the variation coefficient was 8.0 +/- 1.5%). The nature of the neutrophil-stimulating effect of staphylococci and its relationship to the exploratory reactions of phagocytes are discussed.  相似文献   
107.
108.
109.
110.
设为首页 | 免责声明 | 关于勤云 | 加入收藏

Copyright©北京勤云科技发展有限公司  京ICP备09084417号